Turbine-tip arrowhead

ABSTRACT

The present invention is a turbine tip arrowhead, used either strictly as a field point or as the forwardmost tip in conjunction with any prior art broadhead assembly. The key feature of this turbine tip is the geometry, which includes a tapered tip and a plurality of helical rifles, consisting of either grooves or ridges, beginning at the tip of the field point and spiraling back towards the aft end. All rifles spiral in the same rotational direction giving the appearance of a turbine. This turbine tip design provides excellent rotation of the arrow shaft during flight without producing a large amount of aerodynamic drag. The invention is compatible with all contemporary arrow shafts and with all contemporary broadhead assemblies. A novel broadhead assembly utilizing the turbine tip and deployable blades to produce axial rotation is also described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of archery. Specifically, theinvention relates to arrowheads found on arrow devices.

2. Description of the Prior Art

Arrowheads and their associated aerodynamics are a key element forpredictable flight of arrow assemblies. Prior art arrowheads can bebroadly divided into two groups: those with little or no aerodynamiceffect, such as the common field point, and those that do have apronounced aerodynamic effect, whether intended or not, such asbroadhead arrowheads.

Field point arrowheads are very simple devices that are commonly usedfor target practice. Field point arrowheads taper from a maximumdiameter, equal to approximately the diameter of the arrow shaft, downto a point at the forwardmost end. Some variations of the simple fieldpoint geometry include three or four scallops in the field pointsurface. However these scallops are meant to provide a sharper point forpenetration, not influence the aerodynamics of the arrow assembly. Thissimple point in all its prior art embodiments disturbs the air verylittle as the arrow assembly flies towards its intended target. Aconsiderable drawback of the prior art field point is that the arrowassembly flight is governed entirely by the aerodynamics of the vanes atthe aft end of the arrow. The arrow is essentially pushed through theair. This pushing can cause the flight path of the arrow to wander asthe arrow is affected by random influences such as crosswind,oscillating vibration of the arrow shaft, and asymmetries between thearrow vanes. What the prior art lacks is a field point that is itselfcapable of stabilizing the flight of the arrow assembly.

Broadhead arrowheads were invented to increase effective huntingpenetration and success potential. Typically two to four flat,triangular blades are arranged around the forward pointed tip. As thearrowhead enters the intended target, the blades slice a region muchgreater than a simple field point and increase the probability ofinflicting mortal damage upon the intended target. These broad, flatblades have a pronounced aerodynamic effect that can radically affectthe overall stability of the arrow in flight and significantly reducethe precision of flight. The forwardmost tip of such broadheads istypically either the flat blade itself, such as in the patents of Newnam(U.S Pat. No. 5,636,845) or Musacchia (U.S. Pat. No. 4,621,817); or theforwardmost tip is a field point-like cap that provides no aerodynamiceffect, such as in the patents of Adams, jr. (U.S. Pat. No. 6,077,180)or Martinez, et. al. (U.S. Pat. No. 6,319,161). One recent improvementis the broadhead of Kuhn (U.S. Pat. No. 6,663,518) which employs bladeswhose geometry imparts an axial rotational spin on the arrow assemblyduring flight. However, the forwardmost tip of this broadhead is stillbasically a field point.

Mechanical broadhead arrowheads were developed to address problemsassociated with traditional bladed broadheads. Mechanical broadheadsinclude deployable bladed or spiny bleeder appendages that remainclosely attached to the main body of the arrowhead from release untilimpact. This reduces the overall aerodynamic effect of large, bladedstructures during flight. Upon deployment, such appendages providegreater cutting surfaces and or means for lodging within the woundedtarget than a simple flat blade. Again, the forwardmost tip of suchprior art broadheads is typically a field point-like cap, such as in thepatents of Liechty, II (U.S. Pat. No. 6,171,206) and Maleski (U.S. Pat.No. 6,217,467), which provides no aerodynamic effect.

SUMMARY OF THE INVENTION

The present invention is a turbine tip arrowhead, used either strictlyas a field point or as the forwardmost tip in concert with any prior artbroadhead assembly. The key feature of this turbine tip arrowhead is thegeometry, which includes a tapered tip and a plurality of helicalrifles, consisting of either grooves or ridges, beginning at the tip ofthe field point and spiraling back towards the aft end. All riflesspiral in the same rotational direction giving the appearance of aturbine. This turbine tip design provides excellent rotation of thearrow shaft during flight without producing a large amount ofaerodynamic drag. The invention is compatible with all contemporaryarrow shafts.

When used as a replacement for the common field tip-like caps found onprior art broadhead assemblies, the turbine tip of the present inventionagain provides stabilizing, axial rotation of the arrow regardless ofwhether or not the broadhead main blades provide any axial rotationthemselves. The rifling also inflicts additional damage while augeringinto the target upon impact. The invention is compatible with allcontemporary broadhead assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an oblique view of the rifled turbine tip arrowhead of thepresent invention.

FIG. 2 shows an exploded view of the rifled turbine tip arrowhead of thepresent invention used in concert with a mechanical broadhead arrowhead.

FIG. 3 shows a side view of the rifled turbine tip of the presentinvention used in concert with a mechanical broadhead arrowhead in theclosed position.

FIG. 4 shows a front and sectional view of the rifled turbine tip of thepresent invention used in concert with a mechanical broadhead arrowhead.

FIG. 5A shows an oblique view of the rifled turbine tip of the presentinvention used in concert with a mechanical broadhead arrowhead in theclosed position.

FIG. 5B shows an oblique view of the rifled turbine tip of the presentinvention used in concert with a mechanical broadhead arrowhead in theopen position.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, field point 1 of this invention comprises atypically cylindrical body 2 with a maximum diameter approximately equalto the maximum diameter of an arrow shaft. Body 2 is typicallysymmetrical about a longitudinal axis. A portion of body 2 tapers to apoint 3 at one end. A plurality of helical rifles 4, consisting ofeither grooves or ridges, begin at point 3 of the field point 1 andspiral down the longitudinal axis of body 2. Rifles 4 may spiral downthe entire axial length of body 2 or may terminate partially down aportion of the axial length of body 2. All rifles 4 spiral in the samerotational direction giving the appearance of a turbine. In thepreferred embodiment, rifles 4 are placed close together around body 2so that they contact each other down their entire helical length.

In the preferred embodiment there are between about three and about tenrifles 4 located symmetrically about the longitudinal axis of body 2.There are optimally about eight rifles 4 located symmetrically about thelongitudinal axis of body 2. Too few rifles 4 will not provide enoughrotational torque to produce the desired axial flow turbine aerodynamiceffect. Too many rifles 4 must be so narrow or small that theiraerodynamic effect becomes inconsequential as their aggregate surfaceapproaches that of a smooth field point.

Rifles 4 are defined as grooves if the maximum diameter of the rifledportion of body 2 does not exceed the nominal maximum diameter of body2. In other words, body 2 is tapered continuously from aft to point 3and rifles 4 are cut into this otherwise smoothly tapered point. Rifles4 are defined as ridges if the maximum diameter of the rifled portion ofbody 2 exceeds the nominal maximum diameter of body 2. Typically, rifles4 will be V-shaped in cross section although other geometries would beobvious to one of ordinary skill in the art.

Field point 1 also includes an attachment means 5 used to mount fieldpoint 1 on a contemporary arrow shaft. Typically, attachment means 5comprises a male-threaded post that is received by a female-threadedsocket in the arrow shaft. However, attachment to an arrow shaft maycomprise any method common in the art such as a press-fitting or gluing.In these embodiments, attachment means 5 of field point 1 may be asmooth socket or other means for mechanical engagement of the arrowshaft. Field point 1 may be made of any suitable material, such as, butnot limited to, steel, aluminum, plastic, etc.

One of the features of the field point arrowhead of this invention isits ability to produce stabilized arrow flight without the use offletching or tail fins (or feathers). The rotation induced in the arrowby the aerodynamically designed turbine tip is sufficient to stabilizethe arrow in flight. Eliminating or reducing the size of the fletchingin fact improves flight characteristics because the rotational dragnormally induced by the fletching is avoided. It should be noted,however, that all embodiments of the arrowhead of the invention can beused with fletched arrow shafts as well.

The standalone point described above may be used in concert with anyconventional broadhead. A conventional broadhead, as broadly defined,includes a ferrule, at least one blade coupled to the ferrule, a meansfor attachment of the broadhead to an arrow shaft, and a tip. In such acase, the cylindrical, pointed tip common on many contemporarybroadheads is replaced by a tip having the same rifled geometry as thestandalone point of the present invention.

One such novel broadhead, incorporating the turbine tip of the presentinvention, is described in FIGS. 2 through 5B, broadhead arrowheadassembly 100 includes a rifled tip 101 as an alternate embodiment of theinvention. Analogous to the stand-alone field point 1, tip 101 istypically cylindrical in geometry with a maximum diameter at its aft end104 approximately equal to the mating diameter of the first end portion108 of broadhead body 107. A portion of tip 101 tapers to a point 102 atone end. A plurality of helical rifles 103, consisting of either groovesor ridges, begin at point 102 of tip 101 and spiral down thelongitudinal axis of tip 101. Rifles 103 may spiral down the entireaxial length of tip 101 or may terminate partially down the axial lengthof tip 101. All rifles 103 spiral in the same rotational directiongiving the appearance of a turbine. In the preferred embodiment, rifles103 are placed close together around tip 101 so that they contact eachother down their entire helical length. The aft end 104 of tip 101includes a smooth, hollow socket capable of accepting a tensioner 105and capable of fitting over part of first end portion 108 in an integralassembly. Mating surfaces of aft end 104 and first end portion 108 maybe assembled by press-fitting, swaging, gluing, by complementary threadson the mating surfaces, or by any other means common in the art.

Broadhead arrowhead 100 further comprises a body or ferrule 107. At afirst, or proximal, end, ferrule 107 incorporates a first end portion108. First end portion 108 typically tapers to a reduced diameter at itsmost proximal end. Ferrule 107 also has a second, or distal, end portion113. Second end portion 113 is of reduced diameter so that it may fitwithin the hollow end of a conventional arrow shaft. The aft portion offerrule 107 may be slightly flared outwardly. It is not necessary thatthe aft portion of ferrule 107 be flared outwardly, however. As shown inthe embodiment of FIGS. 2 through 5B, the aft portion of body 107 maycontinue substantially straight along its length until the reduceddiameter of second end portion 113. Ferrule 107 is typically symmetricalabout a longitudinal axis between first end portion 108 and second endportion 113. Arrowhead body 107 may be made of any suitable material,such as, but not limited to, steel, aluminum, plastic, etc.

A mounting stub 114 extends rearwardly from second end portion 113 ofarrowhead body 107. Typically, stub 114 is symmetrical about and coaxialwith a longitudinal axis. Mounting stub 114, along with second end 113,is intended to fit into a mating recess typically located at one end ofa standard arrow shaft. Stub 114 may be threaded to mate with matchingthreads in the arrow shaft recess or it may be seated in the recess in apress fit arrangement. Alternatively, mounting stub 114 may be glued orotherwise sealed into the mating recess of the arrow shaft.

In other variations of mounting means, instead of a stub 114, second end113 of body 107 may be of diameter equal to or greater than that of anarrow shaft. Second end 113 may then be hollowed out to fit over saidarrow shaft. In such an arrangement, the inside of hollow second end 113may be threaded to mate with threads on the outer surface of the arrowshaft; or distal second end 113 may be press fit over the arrow shaft.Alternatively, second end 113 may be fitted over the end of the arrowshaft and glued or otherwise sealed to the arrow shaft.

A second key feature of broadhead arrowhead 100 is the inclusion ofmechanically deployable blades 121 including an inertial triggermechanism that both inhibits premature deployment during release andflight yet also facilitates deployment during impact with the intendedtarget. Such a trigger is also found in the pending application of Kuhn(U.S. patent application Ser. No. 10/766,664). Each deployable blade 121comprises an elongated third blade portion 123 that is sharpened on theside adjacent to body 107 when in the closed position. Integral to afirst end of third blade portion 123 is a semi-circular, cam-shapedfourth blade portion 120. Integral to a second end of third bladeportion 123 is a flag-shaped fifth blade portion 124. Fifth bladeportion 124 comprises between about 20% and 50% of the total length ofdeployable blade 121.

Both elongated third blade portion 123 and integral cam-shaped fourthblade portion 120 are disposed in a plane at least substantiallyparallel to a longitudinal axis of body 107. Flag-shaped fifth bladeportion 124 extends from third blade portion 123 at an angle thereto.Fifth blade portion 124 is preferably continuously curved, with a radiusof curvature optimally between about 0.2″ and 0.5″, giving the blade thecharacteristics of an airfoil. The radius of curvature may vary over thesurface of the blade. In the preferred embodiment, fifth blade portion124 curves out of the plane of third blade portion 123 at a constantradius of curvature. The resultant leading edge region of fifth bladeportion 124 is disposed at an angle to body 107 and also at an angle tothird blade portion 123. This angle may be as great as 45 degrees ormore, but optimally it is the range between approximately 5 and 5degrees and most optimally in the range between approximately 5 and 25degrees. In the closed position, fifth blade portion 124 resembles aswept forward wing.

Broadhead assembly 100 includes at least one associated deployable blade121 and preferably three deployable blades 121. Cam-shaped fourth bladeportion 120 fits into a deployable blade slot 110, which is cut into theside of ferrule body 107. Deployable blade slot 110 is substantiallycoplanar with a longitudinal axis of body 107 and is of a depth andgeometry that permits deployable blade 121 to rotate freely about apivot shaft 112 between the open position and the closed position asshown particularly in FIG. 5A and FIG. 5B. In the preferred embodiment,pivot shaft 112 is a removable screw that permits easy replacement ofdeployable blade 121. Pivot shaft 112 is preferably perpendicular to themajor plane of cam-shaped fourth blade portion 120. Deployable blades121 and pivot screws 112 may be made of any suitable material, such as,but not limited to, steel, aluminum, plastic, etc.

As shown in the preferred embodiment in FIG. 4, deployable blade slots110 and their associated deployable blades 121 are preferrably disposedsubstantially symmetrically around body 107 at an angle θ from eachother when broadhead assembly 101 is viewed from the front.

Each of the fifth blade assembly portions 124 are angled out of theplane of their respective third blade portion 123 in the same rotationaldirection as shown in FIG. 4. Fifth portions 124 of deployable blades121, acting together with rifles 103 of tip 101, form an axial-flowturbine. It will be understood by those skilled in the art that allrifles 103 and fifth blade assembly portions 124 are preferably angledin the same rotational direction to promote stable flight.

FIG. 4 shows rifles 103 and fifth portions 124 of deployable blades 121angled clockwise when viewed from the front. Alternatively, rifles 103and fifth portions 124 of deployable blades 121 can be angledcounterclockwise when viewed from the front.

Ferrule 107 further comprises an inertial trigger mechanism that bothinhibits premature deployment of deployable blades 121 during releaseand flight, yet also promotes deployment of deployable blades 121 duringimpact with a target. Cylindrical cavity 109 begins at the leading faceof the first end 108 of body 107 and continues down the longitudinalaxis of body 107 to a depth approximately equal to the location of pivotshafts 112. The diameter of cylindrical cavity 109 is preferably in therange of 20% and 80% of the diameter of tip 101 and most preferably inthe range of 25% and 50% of the diameter of tip 101. Cylindrical cavity109 is symmetrical about the longitudinal axis of body 107.

Trigger 106 comprises a solid cylinder of outer diameter slightly lessthan the inner diameter of cylindrical cavity 109 such that trigger 106can slide freely within cylindrical cavity 109 without binding orbecoming cocked. Trigger 106 includes a trailing surface that interfaceswith ledges 122 on both cam-shaped fourth blade portions 120 whendeployable blades 121 are in the closed position. In the preferredembodiment, trigger 106 is a normal, right cylinder with wallsperpendicular to its flat trailing surface. In this embodiment, ledges122 are also flat so that they contact trigger 106 along their entirelength when deployable blades 121 are rotated into the closed position.Trigger 106 may be made of any suitable material, such as, but notlimited to, steel, aluminum, plastic, etc. Trigger 106 may also becoated with a lubricant, such as graphite, silicone oil, mineral oil,polytetrafluoroethylene, etc., in order to inhibit friction or bindingalong the inner surface of cylindrical cavity 109.

A mechanical tensioner 105 is located between the leading face oftrigger 106 and the socketed aft end 104 of tip 101 and withincylindrical cavity 109. When tip 101 is integrated into broadheadassembly 100, the socketed aft end 104 of tip 101 compresses tensioner105, which in turn urges trigger 106 in the aft direction and down uponledges 122 of deployable blades 121. Tensioner 105 may comprise a coiledspring, a plug of reversibly compressible material, such as solidsilicone, a collapsible volume filled with a compressible fluid, or anyother means for storing mechanical energy that would be apparent to oneof ordinary skill in the art.

During release and flight, inertial forces act to relieve compression ontensioner 105, thereby further urging trigger 106 in the aft directionand firmly retaining deployable blades 121 in the closed position bypressing firmly upon ledges 122. In the closed position, third bladeportions 123 of deployable blades 121 are in close contact with thesides of ferrule body 107. Flag-shaped fifth blade portions 124 aredisposed at angles laterally outward away from the sides of body 107.

During impact, flag-shaped fifth portions 124 of deployable blades 121are forced laterally outward by contact with the surface of the target.At the same time, as rapid deceleration of the broadhead is occurring,trigger 106 is urged forward away from ledges 122 thereby compressingtensioner 105. The combination of torque applied by fifth blade portions124 contact with the target and relieved rearward pressure applied bytrigger 106 permits deployable blades 121 to overcome the engagementbetween ledges 122 and trigger 106 and rotate about pivot screws 112toward the rear as shown in FIG. 4 and FIG. 5B.

The angle of deployment is limited by eventual contact betweendeployable blades 121 with ring 115. In the preferred embodiment, themaximum angle of deployment for blades 121 is preferably in the range ofapproximately 90 degrees and 170 degrees and more preferably in therange of approximately 100 degrees and 135 degrees as measured from theclosed position. In the closed position, third blade portions 123 liealongside body 107 and parallel to the longitudinal axis of body 107.

In the embodiment shown, ring 115 comprises a flat, annular device withan inner diameter equal to the outer diameter of second end 113 of body107 and an outer diameter equal to the outer diameter of body 107. Ring115 is placed over second end 113 prior to attaching second end 113 toan arrow shaft. Alternatively, ring 115 can be mechanically attached tobody 107 by any means common in the art such as welding or adhesivebonding. Ring 115 may also be integrally formed along with body 107.Ring 115 may be made from any material such as steel, aluminum, plastic,etc., although metal is used in the preferred embodiment.

One of the features of the arrowhead of this invention is its ability toproduce stabilized arrow flight without the use of fletching or tailfins (or feathers). The rotation induced in the arrow by theaerodynamically designed turbine tip used in combination with thedeployable blades is sufficient to stabilize the arrow in flight.Eliminating or reducing the size of the fletching in fact improvesflight characteristics because the rotational drag normally induced bythe fletching is avoided. It should be noted, however, that allembodiments of the arrowhead of the invention can be used with allfletched arrow shafts as well.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

1. An arrowhead comprising: a body; a plurality of helical riflesintegral to said body; and an attachment means used to mount saidarrowhead on a contemporary arrow shaft; wherein a portion of said bodytapers to a point at one end; wherein said rifles begin at said pointand spiral down the longitudinal axis of said body; and wherein all saidrifles spiral in the same rotational direction giving the appearance ofa turbine.
 2. An arrowhead according to claim 1, wherein said rifles areclose together around said body so that they contact each other downtheir entire helical length.
 3. An arrowhead according to claim 1,wherein there are between about three and about ten said rifles.
 4. Anarrowhead according to claim 1, wherein there are eight said rifles. 5.An arrowhead according to claim 1, wherein said rifles are defined asgrooves if the maximum diameter of the rifled portion of said body doesnot exceed the nominal maximum diameter of said body, and wherein saidrifles are defined as ridges if the maximum diameter of the rifledportion of said body exceeds the nominal maximum diameter of said body.6. An arrowhead according to claim 1, wherein said rifles terminatepartially down a portion of the axial length of said body.
 7. Anarrowhead according to claim 1, wherein said attachment means comprisesa threaded post.
 8. An arrowhead according to claim 1, wherein said bodyis cylindrical.
 9. A broadhead arrowhead comprising: a ferrule, at leastone blade coupled to said ferrule, an attachment means used to mountsaid broadhead on an arrow shaft, and a tip; wherein said tip furtherincludes a plurality of helical rifles integral to said tip; whereinsaid tip further includes an attachment means used to mount said tip onsaid broadhead; wherein a portion of said tip tapers to a point at oneend; wherein said rifles begin at said point and spiral down thelongitudinal axis of said tip; and wherein all said rifles spiral in thesame rotational direction giving the appearance of a turbine.
 10. Anarrowhead according to claim 9, wherein said rifles are close togetheraround said body so that they contact each other down their entirehelical length.
 11. An arrowhead according to claim 9, wherein there arebetween about three and about ten said rifles.
 12. An arrowheadaccording to claim 9, wherein there are eight said rifles.
 13. Anarrowhead according to claim 9, wherein said rifles are defined asgrooves if the maximum diameter of the rifled portion of said body doesnot exceed the nominal maximum diameter of said body, and wherein saidrifles are defined as ridges if the maximum diameter of the rifledportion of said body exceeds the nominal maximum diameter of said body.14. An arrowhead according to claim 9, wherein said rifles terminatepartially down a portion of the axial length of said body.
 15. An arrowcomprising: an arrowhead body; a plurality of helical rifles integral tosaid body; and an attachment means used to mount said body on acontemporary arrow shaft; wherein a portion of said body tapers to apoint at one end; wherein said rifles begin at said point and spiraldown the longitudinal axis of said body; and wherein all said riflesspiral in the same rotational direction giving the appearance of aturbine; and a shaft devoid of fletching, said arrowhead being securedto one end region of said shaft.
 16. A broadhead arrow comprising: aferrule, at least one blade coupled to said ferrule, an attachment meansused to mount said broadhead on an arrow shaft, and a tip; wherein saidtip further includes a plurality of helical rifles integral to said tip;wherein said tip further includes an attachment means used to mount saidtip on said broadhead; wherein a portion of said tip tapers to a pointat one end; wherein said rifles begin at said point and spiral down thelongitudinal axis of said tip; and wherein all said rifles spiral in thesame rotational direction giving the appearance of a turbine; and ashaft devoid of fletching, said arrowhead being secured to one endregion of said shaft.
 17. A broadhead arrowhead comprising: a ferrulehaving a first end and a second end; at least one deployable bladeassembly, each coupled to said ferrule by a pivot shaft; a mountingmeans for mounting said arrowhead to an arrow shaft; and a tip; whereinsaid tip further includes a plurality of helical rifles integral to saidtip; wherein said tip further includes an attachment means used to mountsaid tip on said broadhead; wherein a portion of said tip tapers to apoint at one end; wherein said rifles begin at said point and spiraldown the longitudinal axis of said tip; and wherein all said riflesspiral in the same rotational direction giving the appearance of aturbine; wherein said deployable blade assembly further comprises asemi-circular fourth blade portion integral to a first end of anelongated third blade portion, and a flag-shaped fifth blade portionintegral to a second end of said third blade portion; wherein saidferrule further comprises a deployable blade slot cut into the side ofsaid ferrule for each said deployable blade assembly; wherein saidfourth blade portion fits into said deployable blade slot; wherein saiddeployable blade slot is substantially coplanar with a longitudinal axisof said ferrule and is of a depth and geometry that permits each saiddeployable blade to rotate freely about said pivot shaft; wherein saidferrule further comprises a cylindrical cavity that begins at theleading face of said first end of said ferrule and continues down alongitudinal axis of said ferrule to a depth approximately equal to thelocation of said at least one pivot shaft; wherein said cavity containsa trigger, comprising a solid cylinder such that said trigger can slidefreely within said cavity; wherein said trigger includes a trailingsurface that interfaces with a ledge on each said fourth blade portionwhen said deployable blades are in the closed position; and wherein saidcavity further contains a mechanical tensioner located between theleading face of said trigger and the trailing edge of said main bladesuch that said trailing edge of said main blade compresses saidtensioner, which in turn urges said trigger in the aft direction.
 18. Anarrowhead according to claim 17, wherein both said third blade portionand said fourth blade portion are disposed in a plane at leastsubstantially parallel to a longitudinal axis of said ferrule and saidfifth blade portion extends at an angle to the plane of said third bladeportion; and said fifth blade portion is preferably continuously curved,wherein said deployable blade assembly has an airfoil-type shape.
 19. Anarrowhead according to claim 18, further comprising a plurality of saiddeployable blade assemblies disposed substantially symmetrically aroundthe longitudinal axis of said ferrule.
 20. An arrowhead according toclaim 19, wherein said fifth blade portion has a leading edge regiondisposed at an angle to said ferrule.
 21. An arrowhead according toclaim 20, wherein said leading edge region is disposed at an angle tosaid ferrule in the range of about 5 degrees and about 45 degrees. 22.An arrowhead according to claim 19, wherein said fifth blade portion hasa length of between 20% and 50% of the overall length of said deployableblade assembly.
 23. An arrowhead according to claim 19, wherein saidcontinuously curved fifth blade portion has a radius of curvature ofbetween about 0.2″ and 0.5″.
 24. An arrowhead according to claim 19,further comprising means for limiting the deployment angle of saiddeployable blade assemblies.
 25. An arrowhead according to claim 24,wherein said means limits the maximum deployment angle of saiddeployable blade assemblies in the range of about 90 degrees and 170degrees.